It is possible to diagnose subarachnoid hemorrhage through a CT-like imaging process performed by using an X-ray diagnosis apparatus. In contrast, it is difficult to diagnose cerebral infarction through a CT-like imaging process performed by using an X-ray diagnosis apparatus and a contrast agent. For this reason, to diagnose cerebral infarction, a perfusion process is performed by using an X-ray Computed Tomography (CT) apparatus and a contrast agent. In the following sections, the perfusion process performed by using an X-ray CT apparatus and a contrast agent will be referred to as a CTP process as appropriate. During the CTP process, three-dimensional blood vessel images in a time series are reconstructed so as to use the reconstructed images for diagnosing cerebral infarction.